I can recommend Beyerdynamic's DT1350 with output 1. All the switches on the BH play well with them too, unlike a fair amount of headphones. So far from my inventory with the BH i would rate Etymotic ER-4P>Beyer DT1350>Vsonic GR07. This is in terms of a reference sound, i.e. least coloration as possible. I'm finding that the DT1350's respond amazingly well to EQ too. I love turning them into the Beyerdynamic T1 with Accudio, very similar

Tokendog, if i may ask you how you feel about headphones sound compared to proper speakers? Since getting onto portable i begin to toy with the idea of adding dedicated earphone tubey amp and a pair of good helmets so i can listen to the music in cabinet room when my wife had enough highend decibels shaking her brain? :-)

Do you think it is possible to achieve naturalness and live dimension with good helmets? Till now i was skeptical but reading here some enthusiasts i begin to think i am not right about bashing earphones.

Denon D2000 (not so much synergy, but it does clean up the bass by having SF switch on)

Sony XB500 (switch both SF and LF on for this one)

The BH can't keep things clean and clear at very high volume (and I must say... I listen pretty loud) but... at lower volume, I couldn't detect much of a difference between it and some of the higher-end amps there, so that's saying something.